Patent GB-470840-A (GB)
Title: Circuit arrangement for teleprinter exchange systems
IPC: H04L25/20
Filed: 1935-12-20
Abstract: 470,840. Code telegraphy. LORENZ AKT.-GES., C. Dec. 20, 1935, No. 35346. Convention date, Dec. 21, 1934. [Class 40 (iii)] In telegraph exchange systems, in which the signals are repeated from one subscriber's line to another by a number of relays operating in succession, distortion due to the transit time of the relays is compensated by correcting relays associated with the subscriber's line circuits. The system described involves' a connection between a 2-wire line a<1>, b<1> (line 3) and a 4-wire line a ... d (line 1), the distortion produced in repetition of signals from the line 3 through the exchange being corrected by relays N, Q in the line circuit of the line 1. The 4-wire line circuit is adapted to be readily converted into a 2-wire line circuit (in which the correcting feature is not used) by using one of the correcting relays N to repeat impulses from the line and short-circuiting the other relay Q, the associated resistances Wi8 and Wi9 serving as a balancing network. Calling and transmitting to operator from line 3. Relay R(i) responds to looping the line at the calling substation and lights calling lamp AL1 whereupon the operator throws keys A, W. Relay M starts the motor of the operator's printer and relay G reverses the current in the calling loop to start the subscriber's motor, releases calling relay R, and connects N(i) to the loop the current in which exceeds that in winding N(ii) so that N reverses its contact. The short-circuit on O is thereby removed and the current over A reversed. Relay O operates I which connects the contact of A to the operator's circuit. Telegraphic impulses are repeated by relay N to A which repeats them to D whereby the loop to the operator's teleprinter is interrupted. Extension of connection to line 1 (4-wire). Key F is thrown and key A restored, relays E, G being maintained and relays P and T pulling up. Relay T reverses the current through B(i) of line 1 whereupon N and Q change over to reverse the current on line a, b to call the subscriber, the current over windings (i) of N and Q exceeding the current over windings (ii). When relay L operates on response of the wanted subscriber, X is operated and A reversed, and lamp LS, which was dimly lighted by P and T, is now extinguished. Telegraphic impulses from line 3 are now repeated to B(ii) line 1 and are sent on as double current impulses by correcting relays N and Q. Relay A (line 1) sends impulses of marking current to winding (ii) of B, line 2, which overcome biassing in the spacing direction in winding (i) of B. This results in the marks sent on by B being shortened and the spaces lengthened, due to the transit time of the armature of B. To correct this, it is arranged that B transmits spacing impulses to windings (i) of N and Q which overcome biassing in the marking direction in windings (ii) of these relays. Transmission in the reverse direction takes place by means of relays L, A (line 1) and B, line 3, no correction being provided. The Specification explains graphically, with reference to Figs. 2 to 6 (not shown), the effect of the correcting relays. Changing from' 4-wire to 2-wire operation. The circuit of relays N, Q, line 1, is adapted for two-wire working as shown for line 3 by using the contact of B to repeat impulses to the line and using N to repeat impulses from the line, the windings of Q being short-circuited.